A superseded part number is not a discontinued part. It means the manufacturer has replaced one number with another — usually because the component was revised, standardised across models, or consolidated with a related item. The function is the same; the number is not.
Why manufacturers supersede
- Design revision. A material, tolerance or profile change produces a new number, and the new part normally replaces the old one in service. - Consolidation. Several similar parts across models are merged into one number. - Supply change. A component moves to a different production source and is renumbered. - Kitting. An individually-supplied part is replaced by a kit containing it plus the seals or fasteners that should always be changed with it.
That last case is the one that surprises buyers most often: you order one number and receive a kit with a different number and a higher price, because the single item is no longer supplied on its own.
Supersession chains
Numbers can supersede more than once. A part first issued as number A may be replaced by B, then by C. A buyer holding a ten-year-old component is reading number A off the part, but only C is orderable. Following that chain is the supplier's job, not the buyer's.
How this catalogue handles it
Three rules govern how supersession appears on this site:
1. An obsolete number always resolves. Searching a previous number returns the current part rather than a no-results page. Every number in a chain is indexed as a lookup key against the part that now fills the role. 2. We never duplicate a product to represent a renumbering. One physical component is one catalogue record, carrying every number it has ever been issued under. This is why searching either the old or the new number lands you in the same place. 3. The chain stays visible. Where a part has superseded, the product page shows the history, so you can confirm that the number you are holding is genuinely the ancestor of the part being quoted.
What to do with old stock lists
If you are working from an old parts list, a service manual, or an inventory spreadsheet full of legacy numbers, send the whole list rather than checking numbers one at a time. Our RFQ intake accepts spreadsheet uploads, resolves each number against current supersession data, and returns the current equivalents with the obsolete numbers shown alongside so you can reconcile your own records.
Last reviewed September 2026. This guide is general technical reference. Always work from the manufacturer documentation for your specific engine.